test that parser is oblivious to set of ABIs

Author: Centril

src/test/ui/parser/extern-abi-syntactic.rs

@@ -0,0 +1,17 @@
+// check-pass
+
+// Check that from the grammar's point of view,
+// the specific set of ABIs is not part of it.
+
+fn main() {}
+
+#[cfg(FALSE)]
+extern "some_abi_that_we_are_sure_does_not_exist_semantically" fn foo() {}
+
+#[cfg(FALSE)]
+extern "some_abi_that_we_are_sure_does_not_exist_semantically" {
+    fn foo();
+}
+
+#[cfg(FALSE)]
+type T = extern "some_abi_that_we_are_sure_does_not_exist_semantically" fn();